Did you know these old A4s run fine on 2 cylinders?

[wristwister]

Well ... not quite "fine", a little rough, but still ...

I just finished the rebuild of my A4, and I've been running it up to temp a few times for the break in oil. Sounded slightly rough to me, but hard to tell unmuffled and with no load, so I assumed it was running fine. Then last night, just for kicks, I pulled one plug wire at a time. Pulled #1 wire, no change! I thought "that's odd! You'd think it would run rougher on 3 cylinders. Plugged # 1 back in and repeated with plugs 2, 3 & 4. Each of those resulted in pronounced running roughness. Went back to #1, no change again!

After bit of troubleshooting I found out the #1 plug was bad. Replaced it and now it's running quite smoothly.

Anyway, I just found it interesting that these old beasts run rough but fine on 2 cylinders. Good to know if I'm ever out "there" and lose a cylinder or 2 for any reason.

[JOHN COOKSON]

An A4 will also start on two cylinders. Try putting the spark plug wires on the spark plugs in an incorrect firing order then try starting the engine............

TRUE GRIT

[joe_db]

Well known low power issue. Swap the "right" two plug wires and you get a relatively smooth 50% power engine.

[tenders]

An A4 will also start on two cylinders. Try putting the spark plug wires on the spark plugs in an incorrect firing order then try starting the engine............

TRUE GRIT

No, don't do that. A backfire in a sailboat engine space is an entirely scary event. DAMHIKT.

[sglazebrook]

Accidentally left the #3 & 4 plug wires off and started. It started but I knew immediately what I had done with it running rough and immediately shut it down. Quite amazing actually!